This invention relates to improvements in a dual chamber prefillable syringe, in which predetermined quantities of first and second medicines are liquid-tightly partitioned in a syringe outer cylinder, in a sterilized state, for injection of both the medicines into a mixture in one chamber as a parenteral solution.
Unstable medicine that cannot be stocked as a parenteral solution is generally powdered by lyophilizing in a freeze-drying apparatus. The powdered medicine and a liquid medicine solution for dissolving the powdered medicine are sealed in a sterilized state and stocked, subsequently mixed for injecting, and used as a parenteral solution.
When powdered medicine and liquid medicine are used, a predetermined quantity of liquid medicine sealed in an ampule or a vial is first sucked into a syringe by a syringe needle. Then, the needle is pierced into a rubber plug of a vial in which a predetermined powdered medicine is sealed. The liquid medicine in the syringe is poured into the vial to mix the powdered medicine with the liquid medicine, creating a parenteral solution. The parenteral solution is again sucked into the syringe, the needle is removed from the rubber plug of the vial, and the solution is injected into a patient as it is.
However, this operation is complicated, taking much time. There is a danger of imparting pain to the patient at the time of injecting, due to the slight deformation of the end of the needle pierced into the rubber plug of the vial at the time of piercing. Further, there is also a danger that part of the rubber plug of the vial may be cut out by a syringe needle as finely pulverized rubber pieces which are, in turn, introduced into the needle and hence injected together with parenteral solution into a patient. The needle and/or the parenteral solution may also be contaminated with bacteria and foreign matters in the-atmosphere that are adhered to the rubber plug.
In order to eliminate the above dangers, there has been invented a conventional dual chamber prefillable syringe in which predetermined quantities of powdered medicine and liquid medicine are liquid-tightly partitioned in one syringe in a sterilized state.
As conventional dual chamber prefillable syringes, those of Japanese Utility Model Publication No. 49-14465, FIG. 19, and Japanese Patent Application Laid-open No. 625357, FIG. 20, are known. As shown in FIGS. 19 and 20, in both the dual chamber prefillable syringes, bypass grooves 1c, 2c are recessed on the inner walls 1b, 2b, substantially at the longitudinal centers of syringe outer cylinders 1a, 2a. Sealing plugs 1f, 2f, having smaller thicknesses 1e, 2e than the lengths 1d, 2d of the bypass grooves 1c, 2c, are liquid-tightly engaged at positions near outer cylinder openings 1g, 2g in the syringe outer cylinders 1a, 2a. First inner chambers 1j, 2j are formed between the cylinder ends 1i, 2i, liquid-tightly sealed by a sealing plug h or a stopper t, and the sealing plugs 1f, 2f. Plungers 1k, 2k are liquid-tightly engaged at positions near the outer cylinder openings 1g, 2g to form second inner chambers 1m, 2m between the plungers 1k, 2k and the sealing plugs 1f, 2f.
Since the dual chamber prefillable syringes shown in FIGS. 19 and 20 are constructed in the same configurations as described above, the following prior art will be described with reference to the dual chamber prefillable syringe shown in FIG. 19.
The dual chamber prefillable syringe of FIG. 21 has powdered medicine of a predetermined quantity sealed in a sterilized state in the first inner chamber 1j and liquid medicine of a predetermined quantity sealed in a sterilized state in a second inner chamber 1m. When used, the plunger 1k is pushed forward by a syringe inner cylinder n to raise the hydraulic pressure of the liquid medicine, thereby pressing forward the sealing plug 1f to the bypass groove 1c in the side of the syringe outer cylinder 1a by means of the raised hydraulic pressure. When the plug 1f is thus pressed, and introduced into the region of the bypass groove 1c, the first inner chamber 1j communicates with the second inner chamber 1m so that the inner pressures in both the inner chambers 1j and 1m become uniform, and the plug 1f is hence stopped. When the plunger 1k is further pressed by the syringe inner cylinder n, the liquid medicine is fed into the first inner chamber 1j through the bypass groove 1c, as indicated by an arrow y in FIG. 21. As the plunger 1k contacts the plug 1f, the entire liquid medicine is fed into the first inner chamber 1j, and the liquid medicine is mixed with the powdered medicine in the first inner chamber 1j to produce a parenteral solution.
Since both the powdered medicine and the liquid medicine are filled in advance and sealed in the syringe outer cylinder 1a, they are not contaminated with bacteria, etc., when injected into a patent as a parenteral solution. Therefore, it is best if the powdered medicine is sealed in the first inner chamber 1j, the liquid medicine is sealed in the second inner chamber 1m, and the dual chamber prefillable syringe containing both the powdered and liquid medicines is heated, to be sterilized, by high pressure steam, etc. This simultaneously sterilizes both the powdered and liquid medicines. If the powdered medicine is heat treated, however, its physical properties are varied. Therefore, it is impossible to heat-sterilize the dual chamber prefillable syringe when both the powdered and liquid medicines are partitioned and filled.
Therefore, in the conventional dual chamber prefillable syringe, liquid medicine is filled in a sterilized state in the syringe outer cylinder 1a, medicine liquid is freeze-dried to powdered medicine by a freeze-drying apparatus and held therein in a sterilized state. The sealing plug 1f is engaged at a position near the outer cylinder opening 1g from the bypass groove 1c in the syringe outer cylinder 1a while the syringe is in the freeze-drying apparatus to seal the powdered medicine in a sterilized state in the first inner chamber 1j in the syringe outer cylinder 1a. Thereafter, as shown in FIG. 22, liquid medicine q is transferred from a sterilized sealed vessel, through a pouring pipe p, into the syringe outer cylinder 1a, while powdered medicine s is sealed in a sterilized state in the first inner chamber 1j. The plunger 1k is subsequently sealed at a position near the outer cylinder opening 1g in the syringe outer cylinder 1a, sealing the liquid medicine q in a sterilized state in the second inner chamber 1m in the syringe outer cylinder 1a.
The filling and sealing of the liquid medicine q in the syringe outer cylinder 1a, in which the powdered medicine s is sealed in a sterilized state, is conducted under a sterilized environment, but the working steps are considerably long. Therefore, there has been a danger of contamination of bacteria, etc. of the liquid medicine q, the powdered medicine s and the syringe outer cylinder 1a during the filling and sealing of the conventional dual chamber prefillable syringe.
As described above, the powdered medicine s is sealed in the sterilized state in the first inner chamber 1j in the syringe outer cylinder 1a. To achieve this, after the liquid medicine to be used as powdered medicine s of a predetermined quantity is filled in a sterilized environment in the syringe outer cylinder 1a, a freeze-drying process occurs. The liquid medicine is changed to powdered medicine s in a freeze-drying apparatus, in a sterilized environment. A sealing process inserts a sealing plug 1f into the syringe outer cylinder 1a, at a position near the outer cylinder opening 1g, via the bypass groove 1c, by an insertion rod set in the freeze-drying apparatus.
Since it takes 20 hours or longer to carry out the freeze-drying process in the freeze-drying apparatus (conducting both the freeze-drying process and the sealing process), it is important to improve the production efficiency of the process. In order to improve the production efficiency of the freeze-drying process, it is required to set as many syringe outer cylinders 1a as possible, sealed at the cylinder ends, in the freeze-drying apparatus.
However, since the conventional syringe outer cylinder 1a is long, the number of the syringe outer cylinders 1a to be set in the freeze-drying apparatus is limited. Since the sealing position of the sealing plug 1f is disposed substantially at the center of the outer cylinder 1a, the insertion rod u for inserting the sealing plug if to the sealing position becomes long, as shown in FIG. 23, and the space in the freeze-drying apparatus occupied by the insertion rod u is increased. Hence, there is a problem in that the number of the outer cylinders 1a to be set in the freeze-drying apparatus is limited.